Magnetic recording head of multiple core printed circuit construction

ABSTRACT

A magnetic recording device comprising a row of closely spaced core members each having a separate energization winding wherein each core winding combination is in fixed relationship with a corresponding single-sided printed circuit board, with an end turn and the associated core end thereof being flush with that printed circuit board edge perpendicular thereto which forms part of the device&#39;&#39;s recording surface. The terminations on the respective printed circuits of each winding and its corresponding input leads are cyclically staggered from board to board to allow the boards to be stacked together without increasing the overall length of the stack, thus permitting the cores to be separated by substantially the thickness of the windings only. Means are included for aligning each board with respect to the others and for aligning the device with the recording medium.

nited States Patent Woodward et al.

1541 MAGNETIC RECORDING HEAD OF MULTIPLE CORE PRINTED CIRCUIT CONSTRUCTION [72] Inventors: Jack Thomas Armon Woodward; Edward Graham Jordan, both of Harlow, England [73] Assignee: Standard Telephones and Cables Limited,

London, England [22] Filed: Nov. 5, 1969 [21] Appl. No.: 874,180

[30] Foreign Application Priority Date Jan. 8, 1969 Great Britain ..1,233/69 [52] 11.8. C1 ..346/74 MC, 179/ 100.2 C, 340/1 74.1 F, 346/74 MP [51] lnt.Cl. ..G11b5/20,Gl 1b5/28,Gllb 5/42 [58] Field of Search ..346/74 MP, 74 MC; 340/ 1 74.1 F; a 179/ 100.2 C

[56] References Cited UNITED STATES PATENTS 3,047,866 7/ 1962 Stover ..346/74 MC 3,323,] 16 5/1967 Solyst ..346/74 MC 1 Feb. 8, 1972 9/ 1969 Starr ..346/74 ES 3,470,563 3,487,391 12/1969 Todt... ....179/l00.2 C 3,521,295 7/ 1970 Poole ..346/ 74 MC ABSTRACT A magnetic recording device comprising a row of closely spaced core members each having a separate energization winding wherein each core winding combination is in fixed relationship with a corresponding single-sided printed circuit board, with an end turn and the associated core end thereof being flush with that printed circuit board edge perpendicular thereto which forms part of the devices recording surface. The terminations on the respective printed circuits of each winding and its corresponding input leads are cyclically staggered from board to board to allow the boards to be stacked together without increasing the overall length of the stack, thus permitting the cores to be separated by substantially the thickness of the windings only. Means are included for aligning each board with respect to the others and for aligning the device with the recording medium.

16 Claims, 9 Drawing Figures I PATENTEBFEB} a ma SHEET 1 BF 2 Inventors JACK 7: A. WOODWARD EDWARD (3. JORDAN Maw Agent PATENIEmta a 1912 sum 2 m2 Inventors JACK T. A. WOOOWARD 6. JORDAN Byfl/ /4 Agent EOWARD MAGNETIC RECORDINGIIEAD OF MULTIPLE CORE PRINTED CIRCUIT CONSTRUCTION BACKGROUND OF THE INVENTION The invention relates to magnetic recording devices which have a particular but not necessarily exclusive application in electrographic printing and/or display apparatus and two methods of making such devices.

In electrographic printing and/or display apparatus of the kind. wherein the recording surface'of either a print drum or band is selectively magnetized to form a pattern or latent image or images thereon representative of information contained in a signal applied to the apparatus, and. wherein the print drum or band is passed through or relative to a powder applicator containing magnetic printing powder which is attracted to the electromagnetically formed latent image or images to develop same and to form a powder image which may be viewed at a display position and/or transferred to a permanent record by printing means which form part of the apparatus, the latent magnetic image or images may be inthe form of dot patterns, the spacing between dot centers, which in practice could be as small as say 0.0065 inches, being deter-- mined by the size of the image to be recorded and the size of the dot matrix from which the image is formed. Generally, the

, recording of the required dots in any one of the rows or columns of the dot matrix, i.e., the dots which are respectively associated with a rowor column of the image to be recorded, is effected by a single row of magnetic recording heads, each dot in a row or column of the dot matrix being associated with a separate one of the row of magnetic recording heads. The complete image is recorded by causing relative movement between the recording heads and the recording surface. The construction of a magnetic recording device to accurately ef-. feet the recording of the dot patterns gives rise to numerous problems which are in the main due to the smallness of the spacing which is generally required between the recording heads, the need to utilize a construction which lends itself to batch or mass production without suffering a loss in accuracy on the spacing between and the alignment of the magnetic recording heads, and the production costs.

I SUMMARY OF THE INVENTION The invention provides a magnetic recording device including a plurality of rodlike cores of magnetizable material, aplurality of helical energizing windings each surrounding a respective core in one-to-one correspondence, a plurality of printed circuit boards, each one of which is associated and in a fixed relationship with a separate one of the energizing windings and its respective core, each end of each of the energizing windings being terminated on the associated printed circuit board to which the core winding input leads are also connected, and a support block of nonmagnetic material within which the printed circuit boards and associated cores and windings are encapsulated, the printed circuit boards being stacked together and adapted such that one end of each of said cores is flush with a recording surface of the support block and separated from the, end or ends of adjacent cores by substantially the thickness of the windings only, the end turns of one end of each core winding being substantially flush with the recording surface which is adapted to be adjacent to a recording medium.

The invention also provides a method of making a magnetic recording device including the steps of providing a number of wire magnetic core members, winding a separate energizing winding along a portion of the length of each of said core members; providing a number (equal to the number of said core members) of sheets of insulating material each having a printed circuit of conductive material formed on one of the major surfaces thereof, and means for aligning it relative to the other sheets, the printed circuits being formed in sets of different patterns, each set of printed circuit patterns being such that the printed circuit areas to which the energizing windings and associated input leads are connected are staggered, removing from each one of the set of sheets on which said set of printed circuit patterns are formed those areas thereof which coincide with the locations of said printed circuit areas on the other sheets which form part of the set of sheets, securing each of the core members and its associated energizing winding to a separate one of the sheets of insulating material in a manner such that an end turn of the energizing winding is positioned at one edge thereof in a fixed relationship with the alignment means, stacking said sets of sheets together, one on top of the other, utilizing the alignment means in a manner such, that said one edges of said sheets form one edge of the stack thereby causing the core members to be formed in a straight line, and encapsulating said stack in a body of nonmagnetic material in a manner such that one edge of each of said core members is flush with a'recording surface of said body.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other features according to the invention will be better understood from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1' illustrates a printed circuit board from which the printed circuit boards forming part of the magnetic recording device according to the invention are manufactured,

FIGS. 2A-2D illustrate the printed circuit boards which are manufactured from the board illustrated in the drawing according to FIG. 1,

FIGS. 3A and 3B illustrate in enlarged perspective views part of a printed circuit board and alternative arrangements for mounting thereon the magnetic core and associated energizing winding which form part of the magnetic recording device according to the invention,

FIGS. 4A and 4B illustrate a front elevation and a sectional side elevation of a magnetic recording device according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order that the magnetic recording device according to the invention may be accurately constructed and economically produced either by batch or mass production techniques, it utilizes a printed circuit arrangement at each of the recording head positions. The printed circuit arrangements provide the means for handling the fragile coil assemblies, making the necessary electrical interconnections between the ends of the devices energizing coils and the input leads of the device, obtaining accurate alignment of the devices magnetic cores, controlling the pitch between adjacent magnetic cores, and varying the length of the device, i.e., the number of recording tracks, to suit particular applications.

The basic printed circuit board from which the-printed circuit boards forming part of the magnetic recording device according to the invention are manufactured is illustrated in the drawing according to FIG. 1, and comprises a sheet of insulating material I, for example a thermosetting plastics material having a printed circuit (the shaded areas) of conductive material, for example copper, formed by conventional means on a major surface thereof and two holes formed therein.

As shown in FIG. 1, the printed circuit is formed in four sec tions 3 to 6, with the section 5 and 6 being utilized to effect the interconnections between the core windings and the input leads to the device while the sections 3 and 4 are utilized as spacers between adjacent printed circuit boards.

One of the areas 7 of section 5 is utilized to effect the connection of one end of a core winding to the printed circuit and one of the areas 10 of section 5, of which each is connected to the areas 7 by means of the strip 11, is utilized to effect the connection of an input lead to the printed circuit and thereby to said one end of the core winding. The other end of this core winding is connected to one of the areas 8 of section 6, each of which is connected to the areas 9 of section 6 by means of the strip 12. An input lead is therefore connected to the said other end of the core winding by connecting it to one of the areas 9.

In order to facilitate the stacking of the printed circuit boards to provide the necessary number of recording tracks with the desired intertrack spacing, it is necessary to cyclically stagger the termination positions of the core windings and associated input leads. With the printed circuit board according to FIG. I the termination positions are staggered with a cycle of four boards and the four printed circuit boards which are utilized to effect this are illustrated in the drawings according to FIGS. 2A-2D.

The printed circuit boards according to FIGS. 2A-2D are manufactured from the printed circuit board according to FIG. 1 by removing those parts of the printed circuit board associated with the circuit areas 7 through 10 which are not required to effect the termination of the core windings and associated input leads.

As shown in FIG. 2A, the printed circuit board according to FIG. I has been modified by forming therein the cutouts I2 through 15 which are arranged to leave only the first one of each set of printed circuit areas 7 to 10, i.e., the cutout l2 removes three of the circuit areas 7, the cutout 13 removes three of the circuit areas 8, the cutout l4 removes three of the circuit areas 9 and the cutout l5 removes three of the circuit areas 10.

With the printed circuit board according to FIG. 2B, the second one of each set of printed circuit areas 7 through 10 remains when the cutouts 16 through 23 are formed therein. Thus when this printed circuit board is stacked on top of the printed circuit board according to FIG. 2A the cutouts I6, 20, 18 and 22 will respectively provide clearance for the terminations made on the said first one of each set of printed circuit areas 7 through 10.

Referring to FIG. 2C, the third one of each set of printed circuit areas 7 through 10 remains when the cutouts 24 through 31 are formed in the printed circuit board according to FIG. I. When this printed circuit board is stacked on top of the printed circuit boards according to FIGS. 2A and 2B the cutouts 24, 26, 28 and 30 respectively provide clearance for the terminations made on the said first and second ones of each set of printed circuit areas 7 through 10 respectively of the printed circuit boards according to FIGS. 2A and 2B.

The fourth printed circuit board in the cycle is illustrated in the drawing according to FIG. 2D, wherein it can be seen that the printed circuit board according to FIG. 1 has been modified by forming therein cutouts 32 through 35 which are arranged to leave only the fourth one of each set of printed circuit areas 7 through 10. Thus when this printed circuit board is stacked on top of the printed circuit boards according to FIGS. 2A-2C, i.e., stacked in a position adjacent to the board according to FIG. 2C, the cutouts 32 through 35 respectively provide clearance for the terminations made on the first, second and third ones of each set of printed circuit areas 7 through 10 respectively of the printed circuit boards according to FIGS. ZA-ZC.

In the construction of a magnetic recording device according to the invention this stacking cycle would be repeated using the printed circuit boards according to FIGS. 2A-2D until the desired number of tracks are provided, thus the eutouts 12 through in the printed circuit board according to FIG. 2A respectively provide clearance for the terminations made on the said second, third and fourth ones of each set of printed circuit areas 7 through 10 respectively of the printed circuit boards according to FIGS. 2B-2D.

It should, however, be noted that the staggering of the terminations is not limited to a cycle of four printed circuit boards, any number of printed circuit boards may be utilized within the practical limits of the device provided a corresponding number of printed circuit areas 7 through 10 are provided on the basic printed circuit board. The limit on the number of printed circuit boards that may be utilized is determined by the allowable physical dimensions of the completed magnetic recording device.

FIGS. 3A and 3B illustrate in enlarged perspective views part of a printed circuit board and alternative arrangements for mounting thereon the magnetic core and associated energizing winding. As can be seen from the drawings, the part illustrated is the top left hand corner of the printed circuit board according to any one of the FIGS. 2A through 2D. The magnetic core 36 is of soft iron wire and the energizing winding 37 which is wound along a portion of the length of the core 36 is of thin insulated wire.

Referring to FIG. 3A, the core and winding assembly is secured by a suitable adhesive to the top'edge 38 of the sheet I in a manner such that the end turn of the winding 37 is positioned at the side edge 39 of the sheet I in a fixed relationship with the holes 2. The ends 40 and 41 of the winding 37 are respectively terminated at the printed circuit areas 7 and 8 and secured by a suitable adhesive to the major surface of the sheet I on which the printed circuit is formed.

Alternatively, the core and winding assembly may, as shown in FIG. 38, be secured by a suitable adhesive in a slot 43 which is provided in the sheet I. As before, the assembly is secured in the slot in a manner such that the end turn ofthe winding 37 is positioned at the side edge 39 of the sheet I in a fixed relationship with the holes 2 and the ends 40 and 41 of the wind.- ing 37 are secured to the sheet 1 and respectively terminated at the printed circuit areas 7 and 8. With this arrangement the corner section 42 of the sheet 1 is removed in order to ensure that the end turn of the winding 37 is completely exposed.

When the input leads have been connected to the printed circuit areas 9 and 10 the printed circuit board assemblies, i.e., the printed circuit boards with the core and winding as-. semblies and the input leads connected and secured thereto, are ready for the construction of a magnetic recording device.

FIgS. 4A and 4B respectively illustrate a front elevation and a sectional side elevation of a magnetic recording device according to the invention, the printed circuit details having been omitted from FIG. 4B for clarity. The magnetic recording device illustrated comprises the printed circuit boards 44 with the input leads 47 (enclosed in a single sheath) and the core and winding assembly 45 connected and secured thereto in a manner as illustrated in and described with reference to FIG. 3A, an adjustment and mounting block assembly 46, and the encapsulating material 48.

The adjustment and mounting block assembly 46 which is secured in relation to the printed circuit boards 44 by means of the encapsulating material 48 includes a mounting block 49 provided with a hole 50, a slot 51 which extends from one edge of the block 49 and breaks through into the hole 50, a tapped hole 52 which is arranged at right angles to the plane of the slot 51 and which passes through the two parts of the block 49 located one on either side of the slot 51, a tapped hole 53 which is arranged at right angles to the plane ofthe slot SI and which passes through one of the said two parts of the block 49, and a tapped hole 54 which is coaxial with the tapped hole 53 and which passes through the other one of the said two parts of the block 49. A countersunk headed screw 55 is screwed into the tapped hole 53 before encapsulation, the countersunk head of the screw providing, in conjunction with the encapsulating material 48 in that part of the tapped hole 52 in the said one of the two parts of the block 49, means for keying the adjustment and mounting block assembly 46 to the magnetic recording device. It should be noted that in an alternative arrangement another countersunk headed screw could be provided and screwed into that part of the tapped hole 52 in the said one of the two parts of the block 49 thus in this arrangement the keying of the assembly 46 to the magnetic recording device would be effected with both of the countersunk heads.

As shown in FIGS. 4A and 4B, the assembly 46 also includes a slotted grub screw 56 which is screwed into the tapped hole 54 and which in conjunction the screw 55 provides a differential screw adjustment for the magnetic recording device. The screw 56 is provided with a central hole which is tapped to match the threaded part of the screw 55 which is screwed into the grub screw 56. The number of threads per inch of the external threads of the screws 55 and 56 are different and arranged such that one revolution of the screw 56 causes the screw 55, which is restrained from being rotated, to move in a substantially vertical direction by a desired amount thereby causing the two parts of the block 49 to be sprung apart by this amount. Therefore, when the surface 57 of the block 49. is fixed relative to a datum platen, i.e., as it would be when it forms part of an electrographic apparatus, the adjustment of the screw 56 would cause the magnetic recording head to tilt relative to the datum plane, thereby providing the means of adjusting the gap between the magnetic cores and the recording medium of the electrographic apparatus.

The encapsulation may be carried out either by injection molding techniques, casting or potting, and therefore any injection molding plastic may be used according to the properties required.

In the encapsulation process, the printed circuit boards 44 are stacked into a jig in a'manner as previously outlined, i.e., one on top of the other in the correct cycle, using the holes 2 to effect the correct alignment of the printed circuit boards and thereby ensuring that the array of core and winding assemblies 45 are assembledinto a straight line at a pitch determined by the individual thickness of the boards and the printed circuit. The stacking jig with the required number of printed circuit board 44 in position is then built up to form a cavity of the desired shape, e.g., as shown in FIGS. 4A and 43 around the boards 44. The end plate of-the cavity is clamped up to hold the printed circuit boards 44 at the correct stack length and one of the side plates of the cavity is adapted to hold the adjustment and mounting block assembly 46 in the correct position relative to the printed circuit boards 44.

The cavity is then filled with the encapsulating material by either injection molding techniques, casting or potting. The encapsulating material holds the printed circuit boards together, provides a means for retaining the assembly 46 relative to the printed circuit boards 44 and provides support for that part of each of the cores 36 which extends beyond the energizing windings 37.

After encapsulating, the material over that part of each of the cores 36 is ground away to a precise distance from the one end turn of the energizing winding 37, thereby forming a recording surface for the device whereat a straight line of magnetic cores are exposed. It is very important that the end turns of the energizing windings 37 should be as close as possible to the recording surface of the recording device since the efficiency is dependent to a large extent on how close the ends of the windings are to the recording surface. it should be noted that, providing the continuity of each of the energizing windings 37 is not broken, the windings may even be exposed at the recording surface.

It may be advantageous in cases where it is likely that the core and winding assembly 45 may come loose from the printed circuit board, to provide means in the side plate of the cavity, which is adjacent to one end of each of the cores 36, for keeping the cores 36 in a straight line during encapsulation. This could be effected by providing a line of holes of the correct pitch in the side plate into which the core ends could be fitted and retained during encapsulation.

It can therefore be seen from the above that the encapsulation of the printed circuit board assemblies provides a rugged device, and accurate register of magnetic cores to the mounting faces for the device and a means of varying the external shape of the device or the mounting attachments for the device.

it should, however, be noted that it is not necessary to provide the adjustment and mounting block assembly as part of the magnetic recording device. According to the invention it could be provided as a separate unit and connected to the device after encapsulation or it could form part of the mounting for the device within the apparatus with which it is being used.

As an indication of the dimensions of such a magnetic recording device as described above, if each core wire 36 is 0.004 inches in diameter and the winding wire is 0.001 inches in diameter, than the two ends of adjacent cores can be spaced on approximately 0.006 inches pitch,-center-to-center. Thus a row of individual recording magnetic cores can be spaced at intervals of 0.006 inches approximately.

The cores 36 require low coercivity, high saturation mag netization and are not limited to soft iron. Other materials such as radiometal or mild steel are satisfactory.

While the recording device so far has been referred to in terms of electromagnetic printing only, it will be appreciated that the head structure is also suitable for recording and/or replay heads for other electromagnetic recording processes, such as tape recording and magnetic drum storage.

Although for most applications potting of the printed circuit boards etc., in a plain epoxy resin compound is quite satisfactory it is possible to impregnate the compound with fillers such as amorphous silica to reduce wear of the recording surface. Alternatively air ducts may be drilled or otherwise provided to enable the head to be supported and located on an air bearing if the circumstances permit.

It will be appreciated that the problem of wear is important when the ends of the windings are located virtually at the recording surface of the head. Yet another method of combating wear is to leave the end turns of the windings exposed and to cover the recording surface with a replaceable film of wear resistant materials which should not exceed 0.002 inches in thickness. Material which may be used include wear resistant plastics films. Alternatively the recording surface may have a film of material such as silicon nitride deposited thereon by glow discharge process.

Other potting compounds may be used where the properties of the potting compound may effect the performance of the head. For example, temperature considerations may call for the use of compounds other than epoxy resins.

In order to provide a recording head with a large number of tracks it may, depending on the number of tracks required, be advantageous to utilize a plurality of the recording devices according to the invention coupled together in series.

What is claimed is:

l. A magnetic recording device comprising a plurality of printed circuit boards, a plurality of rodlike cores, and a plurality of helical energizing windings each surrounding a respective core in one-to-one correspondence, each said core being mounted with its respective winding on and substantially in the plane of one of said plurality of printed circuit boards, said printed circuit boards each including a pair of conductive portions having a multisectioned terminal at either end for receiving respectively one end of the associated core winding and the core winding input lead corresponding thereto, said boards being stacked adjacent one another with the multisectioned terminals of each board having all but one section removed in a cyclic staggered manner from board to adjacent board in order to facilitate stacking thereof by staggering the terminal positions and permit thereby a separation between adjacent cores of substantially the thickness of the core windings only, said stacked printed circuit boards being encapsulated in a support block of nonmagnetic material such that one end of each of said cores is flush with a recording surface of the support block, with the end turn of one end of each core winding being substantially flush with said recording surface.

2. A magnetic recording device as claimed in claim 1 including adjustment and mounting means for the support block.

3. A magnetic recording device as claimed in claim 2 wherein the adjustment and mounting means form an integral part of the support block.

4. A magnetic recording device as claimed in ,claim 3 wherein the adjustment and mounting means include a slotted member, said support block being located on one of the faces thereof which is parallel with the slot therein, first nteans for facilitating the securing of the support block to said one face of the slotted member, and second means for controllably causing the two parts of the slotted member situated on either side of the slot therein to be sprung apart in order to effect the position of the recording surface relative to the recording medium.

S. A magnetic recording device as claimed in claim 4 wherein said first means include a first countersunk headed screw which is screwed into a first tapped hole provided in said one face of the slotted member at a position where it breaks through into the slot therein, the countersunk head of the first screw projecting above said one face to provide a means of keying the slotted member to the support block during encapsulation.

6. A magnetic recording device as claimed in claim 5 wherein said first means also include a second countersunk headed screw which is screwed into a second tapped hole provided in said one face of the slotted member, the countersunk head of the second screw projecting above said one face to provide a means of keying the slotted member to the support block during encapsulation.

7. A magnetic recording device as claimed in claim 5 wherein said first means also include a second tapped hole provided in said one face of the slotted member into which said nonmagnetic material flows during encapsulation thereby providing a means of keying the slotted member to the support block.

8. A magnetic recording device as claimed in claim 5 wherein said second means include a third tapped hole which is provided in the face of the slotted member opposite to said one face thereof and which is coaxial with said first tapped hole, and an externally threaded member which is screwed into said third tapped hole and which is provided with a central tapped hole into which said first screw is screwed, and wherein the external threads of said externally threaded member have a different number of threads per inch to the threads of said first screw.

9. A magnetic recording device as claimed in claim 8 wherein the cores are made of soft iron.

10. A magnetic recording device as claimed in claim 9 wherein the printed circuit boards and associated cores and windings are embedded in an epoxy resin potting compound, wherein the epoxy resin potting compound includes an amorphous silica filler material, and wherein the recording surface is covered with a thin film of wear resistant material.

11. A magnetic recording device as claimed in claim 1 wherein the termination positions for the energizing winding and input lead terminations on the printed circuit boards are cyclically staggered.

12. A magnetic recording device as claimed in claim 1 wherein each of the printed circuit boards is comprised of a sheet of insulating material having a printed circuit of conductive material formed on one major surface thereof and in cludes means for aligning that board relative to the other stacked printed circuit boards to effect a substantially straight line of magneticcores.

13. A magnetic recording device as claimed in claim 12 wherein the alignment means are provided by two apertures formed in each of the printed circuit boards, the core and its energizing winding being secured to the printed circuit board in a manner such that an end turn of the energizing winding is positioned at one edge thereof in a fixed relationship with said apertures.

14. A magnetic recording device as claimed in claim 13 wherein the core and its energizing winding are secured to the printing circuit board by bonding them to an edge of the printed circuit board which is adjacent to said one edge thereof, the ends of the energizing winding being bonded to said major surface of the sheet ofinsulating material.

15. A magnetic recording device as claimed in claim 13 wherein the core and its energizing winding are secured to the printed circuit board by forming a slot in said one edge of the printed circuit board substantially parallel with and in close proximity to an edge of the printed circuit board adjacent to said one edge thereof, the core and its energizing winding being located and bonded in the slot and the ends of the cncrgizing winding being bonded to said major surface of the sheet of insulating material.

16. A magnetic recording device as claimed in claim [5 wherein the conductivamaierial is cop per. 

1. A magnetic recording device comprising a plurality of printed circuit boards, a plurality of rodlike cores, and a plurality of helical energizing windings each surrounding a respective core in one-to-one correspondence, each said core being mounted with its respective winding on and substantially in the plane of one of said plurality of printed circuit boards, said printed circuit boards each including a pair of conductive portions having a multisectioned terminal at either end for receiving respectively one end of the associated core winding and the core winding input lead corresponding thereto, said boards being stacked adjacent one another with the multisectioned terminals of each board having all but one section removed in a cyclic staggered manner from board to adjacent board in order to facilitate stacking thereof by staggering the terminal positions and permit thereby a separation between adjacent cores of substantially the thickness of the core windings only, said stacked printed circuit boards being encapsulated in a support block of nonmagnetic material such that one end of each of said cores is flush with a recording surface of the support block, with the end turn of one end of each core winding being substantially flush with said recording surface.
 2. A magnetic recording device as claimed in claim 1 including adjustment and mounting means for the support block.
 3. A magnetic recording device as claimed in claim 2 wherein the adjustment and mounting means form an integral part of the support block.
 4. A magnetic recording device as claimed in claim 3 wherein the adjustment and mounting means include a slotted member, said support block being located on one of the faces thereof which is parallel with the slot therein, first means for facilitating the securing of the support block to said one face of the slotted member, and second means for controllably causing the two parts of the slotted member situated on either side of the slot therein to be sprung apart in order to effect the position of the recording surface relative to the recording medium.
 5. A magnetic recording device as claimed in claim 4 wherein said first means include a first countersunk headed screw which is screwed into a first tapped hole provided in said one face of the slotted member at a position where it breaks through into the slot therein, the countersunk head of the first screw projecting above said one face to provide a means of keying the slotted member to the support block during encapsulation.
 6. A magnetic recording device as claimed in claim 5 wherein said first means also include a second countersunk headed screw which is screwed into a second tapped hole provided in said one face of the slotted member, the countersunk head of the second screw projecting above said one face to provide a means of keying the slotted member to the support block during encapsulation.
 7. A magnetic recording device as claimed in claim 5 wherein said first means also include a second tapped hole provided in said one face of the slotted member into which said nonmagnetic material flows during encapsulation thereby providing a means of keying the slotted member to the support bloCk.
 8. A magnetic recording device as claimed in claim 5 wherein said second means include a third tapped hole which is provided in the face of the slotted member opposite to said one face thereof and which is coaxial with said first tapped hole, and an externally threaded member which is screwed into said third tapped hole and which is provided with a central tapped hole into which said first screw is screwed, and wherein the external threads of said externally threaded member have a different number of threads per inch to the threads of said first screw.
 9. A magnetic recording device as claimed in claim 8 wherein the cores are made of soft iron.
 10. A magnetic recording device as claimed in claim 9 wherein the printed circuit boards and associated cores and windings are embedded in an epoxy resin potting compound, wherein the epoxy resin potting compound includes an amorphous silica filler material, and wherein the recording surface is covered with a thin film of wear resistant material.
 11. A magnetic recording device as claimed in claim 1 wherein the termination positions for the energizing winding and input lead terminations on the printed circuit boards are cyclically staggered.
 12. A magnetic recording device as claimed in claim 1 wherein each of the printed circuit boards is comprised of a sheet of insulating material having a printed circuit of conductive material formed on one major surface thereof and includes means for aligning that board relative to the other stacked printed circuit boards to effect a substantially straight line of magnetic cores.
 13. A magnetic recording device as claimed in claim 12 wherein the alignment means are provided by two apertures formed in each of the printed circuit boards, the core and its energizing winding being secured to the printed circuit board in a manner such that an end turn of the energizing winding is positioned at one edge thereof in a fixed relationship with said apertures.
 14. A magnetic recording device as claimed in claim 13 wherein the core and its energizing winding are secured to the printing circuit board by bonding them to an edge of the printed circuit board which is adjacent to said one edge thereof, the ends of the energizing winding being bonded to said major surface of the sheet of insulating material.
 15. A magnetic recording device as claimed in claim 13 wherein the core and its energizing winding are secured to the printed circuit board by forming a slot in said one edge of the printed circuit board substantially parallel with and in close proximity to an edge of the printed circuit board adjacent to said one edge thereof, the core and its energizing winding being located and bonded in the slot and the ends of the energizing winding being bonded to said major surface of the sheet of insulating material.
 16. A magnetic recording device as claimed in claim 15 wherein the conductive material is copper. 